Audi-book
Loudness, true peak, noise floor, mains hum, bit rate — measured in your browser, set against the ACX requirements, and the file handed back to you fixed.
This application is served by KNPLIV and runs sandboxed: it cannot read your sign-in details, store anything on your device, or send in the background what you type into it. Everything is gone when you leave the page. Like everything published here, it was read over before going online.
An audiobook is refused on figures an author cannot see. Audi-book measures them, every file at once, without anything leaving your device.
Loudness to the ITU-R BS.1770 standard — the unit the platforms speak in. True peak, the one that exists BETWEEN two samples: that is how a file showing −0.1 dB ends up clipping once converted to MP3, and no ordinary meter shows it. The noise floor, mains hum at 50 or 60 Hz, rumble below 80 Hz, and the real bandwidth — which gives away a “high quality” file actually made from a low-bitrate MP3.
Drop the whole book at once: Audi-book compares the chapters against each other. A chapter recorded on another day, three decibels louder, is heard as a step at every change — the commonest complaint about a self-produced audiobook, and visible only from one file to the next.
Every measurement is then set against the ACX requirements, taken from help.acx.com on 6 September 2026 and checked twice: peak, average volume, noise floor, format, sample rate, constant bit rate, length, room tone, channel consistency. The units are ACX’s and no others: where it writes “dB RMS”, nothing is converted into LUFS.
Three states only — blocking, to fix, advice. Never “compliant”. Audi-book decides nothing: only ACX decides.
The report downloads as HTML or as a CSV table, to file away or send to your narrator.